1. Field of the Invention
The present invention relates to a Micro Electro Mechanical System (MEMS) switch and a method of fabricating the same.
2. Description of the Related Art
RF switches of radio frequency (RF) devices using MEMS technology are widely manufactured. The RF switches are devices mainly applied to circuits selecting and transmitting signals and matching impedances in wireless telecommunication terminals and systems in a micro wave band or a millimeter wave band.
U.S. Pat. No. 6,307,169 (inventor: Sun et al.) discloses such a MEMS switch.
The disclosed MEMS switch includes a hinge supporting a membrane type electrode on a substrate. The hinge includes a control electrode connected to the substrate by an anchor, a hinge collar, and a hinge arm set. The control electrode includes a shorting bar that can be separated from and/or connected to the control electrode. In addition, a travel stop is provided between the substrate and the control electrode to prevent a stiction from occurring.
Japanese Publication Pat. No. hei 2001-143595 (inventor: TSUI KUINGU SAN) discloses another example of a MEMS switch.
The disclosed MEMS switch uses a micro plate frame structure suspended on a spring suspension system and formed on a substrate. The spring suspension system includes an end to which an anchor is adhered and extends substantially orthogonally to a signal line. The micro plate frame includes a short piece opposite to a gap in the signal line, and an electric contact point post is formed on the signal line to form a condenser structure. A selected voltage is applied to the condenser structure so that the condenser structure is pulled toward a lower electrode due to a static electricity.
An MEMS switch as described above uses an electrostatic force. Thus, a drive voltage is great and a stiction phenomenon occurs. In the stiction phenomenon, an unintentional adhesion occurs on a surface of a micro structure, and thus a restoration force fails to overcome a force working on a surface such as a capillary force, a Van der Walls force, an electrostatic force, or the like. As a result, the adhesion permanently occurs.
Also, in a case where contact states of the shorting bar disclosed in U.S. Pat. No. 6,307,169 and the short piece disclosed in Japanese Patent Publication No. hei 2001-143595 are poor, signals are not smoothly transmitted, and an insertion loss occurs.